1. Field of the Invention
The present invention relates to a triaxial contact. It also relates to a process for assembling such a triaxial contact. More particularly, it finds use in the field of parasitic-sensitive signal transmissions, especially in the field of telecommunications. A triaxial contact according to the invention may be used, for example, as an Ethernet cable connector. The invention also provides an easy process for assembling such contact.
2. Description of Prior Developments
In prior art, a triaxial contact comprises three contact elements. A first contact element, a cylindrical contact, has a cavity allowing to accommodate a second contact element, an intermediate contact, and a third contact element, a central contact, as well as insulating means. The insulating means are used to insulate contacts from each other. The intermediate contact typically has a socket at a first end, and a pin at a second end. The pin extends along a longitudinal axis of the socket, from a periphery of said socket. The central contact typically has a socket topped by a pin. This central contact is preferably placed in the central position, at the center of the first cylindrical contact, and at the center of the socket of the intermediate contact.
In order to insulate the three contacts from each other, a prior art triaxial contact, as shown in FIG. 1, has a first front insulator, on the right side of the figure. This first front insulator is interposed between an outer surface of the intermediate contact and an inner surface of the first cylindrical contact. The first front insulator is held in the cavity of the first contact by abutment against a release of the inner surface of the first contact. The intermediate contact is held inside the first front insulator by abutment against an inner shoulder of the first front insulator. The intermediate contact is housed in the first front insulator so that the socket is flush with a first side of the first cylindrical contact and that the pin projects out of a second side of the first cylindrical contact, the latter side being opposite to the former.
In order to electrically insulate the intermediate contact from the central contact, the triaxial contact has a second front insulator. The second front insulator especially covers an inner surface of the intermediate contact pin. The second front insulator is held inside the pin, by abutment against the periphery of the pin. The central contact is accommodated in a receptacle of the second front insulator, so that the central contact socket is also flush with the first side of the first cylindrical contact and that the pin of the central contact projects out of the second side.
In order to retain the central contact inside the receptacle of the second front insulator, a third rear insulator is force-fitted over the second front insulator. The third rear insulator allows the passage of the central contact pin, and of the intermediate contact pin, while insulating them from each other. An assembly is composed of the first front insulator, the intermediate contact, the second front insulator, the central contact and the third rear insulator. This assembly is retained inside the cavity of the first cylindrical contact on the one hand by abutment against the release of the inner surface and on the other hand, at the second side of the first contact, by an inwardly turned end of the cavity. Said end of the first contact is turned inwards after introducing the assembly inside the cavity. The turned end of the first cylindrical contact is then punched.
Considering that the intermediate contact is inserted in the first front insulator from a first side, that the second front insulator is inserted in the intermediate contact from the same side and that the central contact is also inserted in the second front insulator from the same side, then, in a certain sense, the assembly is only physically retained inside the first cylindrical contact by said punching. The stacking direction depends on the need to prevent removal of the intermediate contact when a complementary contact is connected. Then, the retention force is of about 50 daN. The different elements composing the triaxial contact are fitted one inside the other in the same fitting direction. Punching must be capable of resisting a pulling force simultaneously exerted on the intermediate contact and on the central contact pins.
A prior art triaxial contact involves a first problem, consisting in that such a triaxial contact includes individual front insulators, which are specific for each contact contained therein. Hence, a prior art triaxial contact having three contacts also has two front insulators. The provision of these two front insulators involves a first problem consisting in that each part is to be molded individually. Therefore, each front insulator has a specific shape which allows stacking thereof. The provision of separate molds is costly. Further, the provision of such number of parts requires a number of assembly steps. Also, the solidity of the assembly is only ensured by punching at an end of the first cylindrical contact. Such punching constitutes an additional step for assembling such a triaxial contact, and also requires special tools.
The invention has the object to obviate the above problems by providing a triaxial contact only comprising two insulators: a front and a rear insulator. The front insulator is used as the main insulator between the three contacts. Said first front insulator is accommodated inside a cavity of the first cylindrical contact. The front insulator further has a first receptacle to accommodate the intermediate contact and a second receptacle to accommodate the central contact. The two receptacles are separate, so that the intermediate contact is electrically insulated from the central contact. The rear insulator insulates the contacts from each other at an end of the first contact, a first socket of the intermediate contact and a second socket of the central contact projecting out of said end.
The arrangement of the invention first consists in providing parts which can be snapped into each other. A triaxial contact according to the invention does not require special assembly tools. In fact, the front insulator has harpoons which can be locked in a complementary receptacle provided on an inner wall of the first cylindrical contact, to form an elastic lock when the front insulator is fitted in the first cylindrical contact. Also, the intermediate contact is held inside the front insulator by a harpoon system provided on the intermediate contact, which is anchored in the front insulator upon assembly. The harpoon of the intermediate contact penetrates the insulator. On the other hand, the intermediate contact is inserted from a first side of the front insulator, whereas the central contact is inserted from a second side, the second side being opposite to the first side. The central contact is held in the rear insulator by a first abutment of the front insulator and by the rear insulator also abutting against an inner release of the first cylindrical contact. This lock is highly strong and the solidity of the assembly is naturally and effectively obtained with a single piece. Hence, the arrangement provided by the invention is less expensive, since it comprises a smaller number of insulating components, and the assembly of the different elements of a triaxial contact according to the invention is simpler and faster since the assembly process includes a smaller number of steps. The assembly can also stand a few disassembly operations, since the intermediate contact can be forcibly removed from the cylindrical contact.
Hence, the invention relates to a contact of the triaxial type, comprising a first outer cylindrical contact, an intermediate contact and a central contact, these contacts being held together by mechanical means and electrically insulated from each other by an insulating member, characterized in that
the insulating member includes a single-piece front insulator, the front insulator being held at a front end of a cavity of the first cylindrical contact by means of a first elastic lock, secured in a first groove,
the intermediate contact is held in a first receptacle of the front insulator by a harpoon embedded in the material of the front insulator,
the central contact is situated in a second receptacle of the front insulator, and is locked therein by a shoulder of the front insulator.
The invention also relates to a process for assembling a triaxial contact including the following steps in the following order:
introducing an intermediate contact in a first receptacle of a front insulator from a front end of the front insulator,
securing a harpoon of the intermediate contact in a wall of this first receptacle,
introducing a central contact in a second receptacle of said front insulator from a rear end of said front insulator, said rear end being opposite to the front end of the front insulator,
engaging a rear insulator against the rear end of the front insulator, the rear insulator and the rear end of the front insulator having an intermediate contact pin and a central contact pin projecting therefrom,
introducing the assembly composed of the rear insulator, front insulator, intermediate and central contacts in a cavity of a cylindrical contact trough a front end of said cylindrical contact,
locking said assembly against a step of the cylindrical contact by securing an elastic lock of the front insulator in a complementary groove of the cylindrical contact.